The present invention relates to a semiconductor device, and in particular to a semiconductor device having a bleeder resistance circuit using thin film resistors and a method of manufacturing the same.
Although a bleeder resistance circuit using a thin film resistor has been widely used, no attention has been paid to wiring on thin film resistors and potentials of electric conductors at lower portion of the thin film resistor, but those in the field are aware that various arrangements are made have been known. Further, polysilicon is used frequently as a thin film resistor material, but that in which, when a MOS transistor is consolidated in the same chip, the film thickness is made equal to the film thickness of a gate electrode of the MOS transistor has been known.
In a conventional bleeder resistance circuit using a thin film resistor, however, there is a known a problem that a voltage division ratio becomes inaccurate frequently. Further, in a conventional bleeder resistance circuit coordinating a MOS transistor in the same chip, there has been such a problem that a resistance value change due to the temperature of a polysilicon thin film resistor (temperature coefficient of a resistance value) being large in a region of high sheet resistance value at 1 kilo-ohm/xe2x96xa1 or higher, and the sheet resistance value has to be set small in order to obtain high voltage division accuracy in a wide temperature range, and thus, the area occupied by the bleeder circuit region requiring a high resistance value at one meg-ohm or higher becomes larger.
It is an object of the present invention to solve the above-mentioned subjects, and provide a bleeder resistance circuit of high accuracy having an accurate voltage division ratio and a small temperature coefficient of a resistance value and a semiconductor device of high accuracy having a small temperature coefficient using such a bleeder resistance circuit, e.g., a semiconductor device such as a voltage detector and a voltage regulator.
The first means adopted for the purpose of achieving the above-mentioned object in a semiconductor device of the present invention is characterized in that the potential of the wiring on a thin film resistor and an electric conductor in the lower part of the thin film resistor in a bleeder resistance circuit using thin film resistors is made almost equal to the potential of respective resistors. This is based on that such a fact that the resistance value of the thin film resistor is changed by the potential of the wiring on the bleeder resistance circuit using thin film resistors (in particular polysilicon thin film resistors) and the electric conductor in the lower part thereof has become clear through experiments by the present inventor.
The second means adopted for the purpose of achieving the above-mentioned object in a semiconductor device of the present invention is characterized in that a polysilicon thin film resistor of a bleeder resistance circuit is made to have a film thickness thinner than a gate electrode of a MOS transistor coordinated in the same chip. This is based on that such a fact that dispersion of the resistance value becomes smaller and temperature dependency of the resistance value becomes lower even at the same sheet resistance as the film thickness of the thin film resistor (in particular polysilicon thin film resistor) gets thinner has become clear through experiments by the present inventor.
According to the semiconductor device of the present invention, it is possible to realize a bleeder resistance circuit of high accuracy having a more accurate voltage division ratio by making the potential of the wiring on the thin film resistor and the electric conductor in the lower part of the thin film resistor of the bleeder resistance circuit using the thin film resistors almost equal to the potential of respective resistors. In particular, when polysilicon is used in the thin film resistors, in the semiconductor device of the present invention, it is possible to control the dispersion of the resistance value and make temperature dependency of the resistance value smaller by making the film thickness of the polysilicon thin film resistor of the bleeder resistance circuit thinner.
It is possible to obtain a semiconductor device of high accuracy having a small temperature coefficient, e.g., a semiconductor device such as a voltage detector and a voltage regulator using such a bleeder resistance circuit.